Layers
Layers are a way of managing, tidying and also controlling the visual layout of a drawing. A whole section of a drawing can be turned on or off, or simply one aspect can be controlled - text for example. This is all done by using layers within Autocad.

The concept of layers is used in other software applications, such as Paintshop programs. For those not aware of the concept, we'll start from the beginning:

When a new Autocad drawing is created, everything which is drawn is drawn on the one default layer, named 0. When creating drawings, the layer 0 shouldn't really be used. New layers should be set up with names corresponding to the content contained on them.

What is a layer?
A layer can be thought of as a large piece of clear plastic, as infinitely large as the drawing area in Autocad. When drawing in Autocad, everything is drawn on the default layer which is set current. Only the objects you are drawing are visible on the layer, the layer itself can never be seen - it is invisible. Each new layer is created by you, the user .Normally, it is acceptable to have a layer for each different part of a drawing. The layers created for a simple house plan could be as follows:

Wall_External
Wall_Internal
Doors
Windows
Fittings
Text_Notes
Dimensions

The separate lines and shapes representing each part of the house would be arranged on its relevant layer above. Each layer could be assigned its own colour so that everything drawn on that layer appeared the same colour.
Remember we said that layers can be used to manage drawings? well for example, in order to see the drawing more clearly, we may want to remove all the text and dimensions from the drawing. We want to keep the information, just remove it from view. Deleting it wouldn't be appropriate as we would lose all of our work! All we have to do is tell Autocad to not display the Text_Notes and Dimensions layers by turning off the layers in layer manager. The layers can then ne turned back on again whenever we choose.

Layers are controlled by the layer properties manager button which is located on the object properties toolbar:





The layer property manager is where all the layers are controlled. The layout above shows a typical use of layers.

From the layer property manager we can:

Add a New Layer - Press the New button to create a new layer.

Delete a Layer - Press the delete button to delete the selected layer.

Set Current layer - Press the current button to set the selected layer current. All objects drawn will then be drawn on this current layer.

Show Details - Press the show details button to see more detailed information about the selected layer.

Each layer also has the following options against it:


Name - Displays the layer name.

On - Controls if the layer is on or off. Select the light bulb to turn the layer off on the drawing.

Freeze in all VP - Pressing this will freeze the layer in all viewports as well as the current model view (see lesson 10 to learn about viewports)

Lock - This handy feature locks a layer preventing any content of the layer from being modified.

Colour - Change this to whichever colour you like. All objects drawn on the layer will display the chosen colour provided that the objects colour setting in the object properties toolbar (shown above) is set to 'By Layer'.

Linetype - Set the default linetype for all objects drawn on the layer. i.e continuous, dashed, dotted etc.

Lineweight - Set the thickness a line appears .Default is no thickness. This option can be toggled on/off on the display by the LWT button above the command console.

Plot - Select if the layer will be shown when the drawing is plotted (printed).

The current layer, layer colour, linetype and lineweight can all be controlled outside of the layer properties manager via the object properties toolbar.

That's it for basic layer controls! Get used to using layers as you will be using them often - especially when you find you need to start managing large drawing files that contain a lot of information.

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